This invention relates to a log debarker, and in particular to a rotary-ring-type log debarker which includes one or more rotary debarker rings that carry pivoted, inwardly biased debarking arms arranged in at least two different sets of arms.
According to the invention, and relative to the longitudinal direction in which a log that is to be debarked is transported, these arm sets are axially offset from one another in the machine, with the arms in each set effecfively occupying a common rotary debarking plane that is normal to the machine""s long debarking axis. The debarking tool tips (or tools of various kinds) borne by the arms in these plural sets thus effectively occupy spaced debarking planes, with all tool tips in each associated set of arms occupying substantially the same plane (one of the mentioned debarking planes). With ring rotation, the arm tools in each set move in the associated rotary debarking plane.
Rotary-ring-type log debarkers have been around for years and are well known in the wood-products industry. It is typical for such a debarker to include a single, rotary, power-driven debarker ring (or rotor) on which there are mounted, typically pivotally, plural, elongate debarking arms, the inner or free ends of which carry appropriate debarking tool tips These tips may take the form, for example, of scraper blades, spinning abrader wheels, or scoring knives.
When there is no log to be debarked in such a machine, the inner ends of the debarking arms (i.e., the tool-tip ends or tool ends) lie very closely adjacent (but not in contact with) one another in a fashion circumsurrounding the long debarking axis of the machine, i.e., that axis along which a log that is to be debarked is conveyed. For each machine, this tool-end condition effectively limits the maximum number of arms which can be carried without the inner arm tips (or other arm parts) hitting one another near the long axis of the machine. It also thus further determines the minimum log debarking diameter which can be handled by a machinexe2x80x94a determination which requires key consideration in today""s world where progressively smaller and smaller logs are being debarked.
Further, because of the fact that maximum practical debarking throughput speed in a debarker of the kind now being discussed is dependent, at least in part, on the number of arms that perform the debarking function (i.e., the more arms, the greater the achievable throughput speed), it is usually desirable to have the maximum number of arms possible.
Among other advantages offered by non-crowding of the center of a debarking ring by tool tips are (a) that more space is furnished for the expelling and removal of bark, and (b) that debarking arms, and/or their associated pivoting structures, such as arm pivot shafts for example, which can be designed as torque tubes to flex appreciably under a debarking load, thus to promote confident xe2x80x9cfollowingxe2x80x9d of log irregularities through the xe2x80x9cmechanismxe2x80x9d of spring-loading andxe2x80x94unloading of the arms/shafts/tubes.
Regarding the important advantages that can be made available via such flexing capability, and considering certain shortcomings of prior art machines, any appreciable flexing of tool arms in current debarkers with closely spaced tool tips is not possible because tool""s then hit one another.
The present invention addresses these considerations in a very satisfactory and practical way by incorporating, into such a machine, plural sets (at least two) of debarking armsxe2x80x94each set being axially offset in the machine along the long axis along which a log moves. Preferably, the arms in each set are equiangularly spaced about the debarking axis, and the arms in the plural sets, when such are viewed along the long debarking axis of the machine, also preferably all appear to be equiangularly displaced about that axis. These plural sets of arms may be carried on a single debarking ringxe2x80x94a circumstance which accommodates the use of, for example, two axially offset sets of armsxe2x80x94or they may be carried on more than two debarking rings or rotorsxe2x80x94a situation in which each debarking rotor can have two or more sets of debarking arms. Where plural rotors are employed, the different rotors can turn either in the same, or different, direction(s).
By constructing a machine in this fashion, for a given debarking-arm tool-tip width, an overall greater number of arms (greater than the number conventionally permitted) can be incorporated without fear of their tool tips colliding with one another. Accordingly, a higher than conventional log throughput rate can be achieved, or, if desired, a log surface can be debarked twice for xe2x80x9ccleanerxe2x80x9d debarking with only one rotor.